Spitzer Observations of Gamma-Ray Burst Host Galaxies: A Unique Window into High-Redshift Chemical Evolution and Star Formation

We present deep 3.6 μm observations of three z ~ 5 GRB host galaxies with the Spitzer Space Telescope. The host of GRB 060510B, at z = 4.942, is detected with a flux density of 0.23 ± 0.04 μJy, corresponding to a rest-frame V-band luminosity of 1.3 × 10^(10) L_☉, or ≈0.15 L_(*,V,z=3). We do not detect the hosts of GRBs 060223A and 060522 and constrain their rest-frame V-band luminosity to